Er–Yb Waveguide Amplifiers in Novel Silicate Glasses

A set of novel silicate glasses containing ZnO and co-doped with ${\hbox {Er}}^{3+}$ and ${\hbox {Yb}}^{3+}$ was designed as substrates for optical waveguide amplifiers. Characterized by exceptionally low up-conversion, minimum Er concentration quenching and high mechanical as well as chemical stability, the reported glasses can compete with phosphate-based materials typically used in the state-of-art active devices. Straight channel waveguides with propagation losses as low as 0.18 dB/cm were fabricated in these substrates using ${\hbox {Ag}}^{+} \Leftrightarrow {\hbox {Na}}^{+}$ and ${\hbox {K}} ^{+} \Leftrightarrow {\hbox {Na}}^{+}$ thermal ion exchange. Net on-chip gain values of 6.7 dB at 1537 nm were measured and a net fiber to-fiber gain of 5 dB was achieved when pumped at 976 nm. A six-level spatially resolved numerical model of an Er–Yb co-doped active waveguide was developed to analyze and optimize the amplifier performance. Modification of the rare-earth dopant concentration and the channel waveguide geometry was proposed to increase the gain figure and improve the overall amplifier efficiency.